1. Technical Field
This invention relates to signal processing systems, and more particularly to systems that estimate pitch.
2. Related Art
Some audio processing systems capture sound, reproduce sound, and convey sound to other devices. In some environments, unwanted components may reduce the clarity of a speech signal. Wind, engine noise and other background noises may obscure the signal. As the noise increases, the intelligibility of the speech may decrease.
Many speech signals may be classified into voiced and unvoiced. In the time domain, unvoiced segments display a noise like structure. Little or no periodicity may be apparent. In the speech spectrum, voiced speech segments have almost a periodic structure.
Some natural speech has a combination of a harmonic spectrum and a noise spectrum. A mixture of harmonics and noise may appear across a large bandwidth. Non-stationary and/or varying levels of noise may be highly objectionable especially when the noise masks voiced segments and non-speech intervals. While the spectral characteristics of non-stationary noise may not vary greatly, its amplitude may vary drastically.
To facilitate reconstruction of a speech signal having voiced and unvoiced segments, it may be necessary to estimate the pitch of the signal during the voiced speech. Accurate pitch estimations may improve the perceptual quality of a processed speech segment. Therefore, there is a need for a system that facilitates the extraction of pitch from a speech signal.